circular_queue.hpp

#include <vector>

template<class T, unsigned buffer_size=500>
class circular_queue
{
public:
	unsigned front = 0;
	unsigned back = 0;
	unsigned count = 0;
	std::vector<T> items;

	circular_queue<T>()
		: items(buffer_size)
	{
	}
	
	~circular_queue<T>()
	{
	}
	
	void push(const T& item)
	{
		if (count >= items.size())
		{
			std::vector<T> newQueue(items.size() * 2);

			unsigned n = items.size() - front;

			memcpy(newQueue.data(), &(items[front]), n * sizeof(T));

			if (front > 0)
			{
				memcpy(&(newQueue[n]), items.data(), front * sizeof(T));
			}

			front = 0;
			back = items.size();

			items.swap(newQueue);
		}
		
		memcpy(&items[back], &item, sizeof(T));

		count++;
		back++;
		if (back >= items.size())
		{
			back -= items.size();
		}
	}
	
	void pop(T& item)
	{
		assert(!empty());
		memcpy(&item, &items[front], sizeof(T));

		count--;
		front++;
		if (front >= items.size())
		{
			front -= items.size();
		}
	}
	
	T& peek()
	{
		assert(!empty());
		return items[front];
	}
	
	bool empty() const
	{
		return count == 0;
	}
};